Capless markers are known in the prior art. Commonly-owned U.S. Pat. No. 6,033,141 is hereby incorporated by reference in its entirety. Generally, these markers provide a retraction and extension carriage to permit the tip of the marker to be concealed within a housing when not in use so as to avoid accidentally contacting clothing or papers when not in use.
Some capless markers include a seal to prevent the drying of the tip due to evaporation of ink into the atmosphere. One such marker is disclosed in the above-referenced patent, U.S. Pat. No. 6,033,141, issued to Blaustein, et al. The marker discloses a single-piece seal mounted adjacent a front cowling. The single-piece seal includes a concave membrane with a slit to permit the extension of the ink cartridge tip for writing and closes upon retraction of the ink cartridge.
A variety of carriage mechanisms may be employed for linear movement of the cartridge within a marker housing. Because the carriage, by necessity, involves moving parts, there is a likelihood that the carriage mechanisms do not provide an airtight closure at the end opposite the writing tip of the marker. Therefore, infiltration of air from the carriage end of the marker can occur despite the placement of a seal adjacent the tip.
There is thus absent from the prior art a retractable capless marker which provides a securely-maintained, airtight chamber of a relatively simple design, which eliminates the need for a separate cap, and which prevents drying of the nib due to air infiltration from either the front or rear end of the marking instrument.